The Chief Rabbi, Sir Jonathan Sacks, issued a rallying cry for Jews today to defend their schools from English law after the court of appeal decided that admission on the basis of a parent's Jewish status was discriminatory. Writing in this week's Jewish Chronicle, he condemned the ruling, saying it branded Judaism "racist".

His comments follow last month's judgment by the court of appeal that a Jewish school that prioritised applications from children with Jewish mothers discriminated on grounds of race. Seen as a landmark decision on the admissions criteria used by faith schools, the case centred on a boy known as M, 12, who was refused admission to JFS, in Brent, London.

M, a Jew who regularly attends a progressive synagogue, was told he could not be admitted because his mother had converted to Judaism in a procedure not recognised by the Chief Rabbi.

Overturning a previous judgment in favour of the school, the court said a policy determining eligibility based on a person's descent, rather than religious practice, amounted to racial discrimination.

Sacks wrote that Jewish education was extended to Jews, "that is, those born of Jewish mothers" or those who had converted according to the standards of the religious authority to which the school belonged. It was a religious, not a racial, test and it applied to all Jewish schools, "Orthodox and non-Orthodox alike".

"An English court has declared this rule racist, and since this is an essential element of Jewish law, it is in effect declaring Judaism racist," Sacks wrote. "To be told now that Judaism is racist is distressing. To confuse religion and race is a mistake."Faith schools are exempted from the law prohibiting discrimination on grounds of religion or belief, to enable them to provide education in line with their beliefs."Once [a faith school] is oversubscribed, it can restrict entry to children whom – or whose parents – it regards as sharing the school's faith," the court said. "No school, however, is permitted to discriminate in its admissions policy on racial grounds."